Neutrinos can decay already within the Standard Model (SM) of particle physics, which was first investigated in Ref. [1]}.
However, it was found that the decay rate exceeds by many orders of magnitude the current age of our Universe, i.e. \(\tau _\nu ^{\mathrm {SM}} \ge (G_{F}^2 m_\nu ^5)^{-1} \gg t_U\) .
First investigation of a possible neutrino decay via a Beyond the Standard Model (BSM) channel was done in Ref. [2]} to explain the at the time present solar neutrino problem, which then, however, was successfully explained by corrections to the neutrino vacuum oscillation probability induced by matter effects.
The increasing experimental sensitivity and especially the in future expected reach motivates a detailed study on the field of neutrino decays to identify the required particle content, coupling strength and mass scale of the involved particles needed to result in \(\tau _\nu \le t_U\) .
